The sun sets on the Greek island of Santorini, Greece, July 2, 2015. The International Monetary Fund delivered a stark warning on Thursday of the huge financial hole facing Greece as angry and uncertain voters prepare for a referendum that could decide their country's future in Europe. REUTERS/Cathal McNaughton

The sun sets on the Greek island of Santorini, Greece, July 2, 2015. The International Monetary Fund delivered a stark warning on Thursday of the huge financial hole facing Greece as angry and uncertain voters prepare for a referendum that could decide their country's future in Europe. REUTERS/Cathal McNaughton